Carboxylic acid esters are used widely in technology. Exemplary uses lie in the field of lubricants and the substrates for cosmetics. Thus, DE 10 2005 052 173 A1 discloses the use of fatty acid-2-ethylhexyl ester mixtures as the oil components in cosmetic and pharmaceutical products.
Numerous methods are known for obtaining carboxylic esters from components containing carboxylic acids, and alcohols. Common to all of these methods is that components containing carboxylic acids, and alcohol are transported separately to the location for the technical esterification or transesterification, and are first brought into contact with one another at the location where the technical esterification is to be carried out. For this in particular, the step of the transshipment of the components containing carboxylic acids is problematic due to its frequently high degree of viscosity, which in typical methods must be carried out at least twice.
With some components containing carboxylic acids having a high melting temperature, a melting is required prior to the transshipment or conversion, as a result of which, the expenditures for this step increase. Examples of such components containing carboxylic acids are pure carboxylic acids such as oxalic acid, which tends to decompose during the melting process, fumaric acid, salicylic acid, palmitic acid, heptadecanoic acid, stearic acid, and arachidic acid, the melting point of which is above 50° C. Long chain carboxylic acids having polyvalent alcohols also exist in the solid state at room temperature. By way of example, at this point glycerin trilaurate, having a melting temperature of 46.5° C., is referenced.
Another disadvantage of this two-step method (first step: separate transport of the reactants to the place of esterification, second step: bringing the reactants into contact with one another at the place of esterification) is the result of the low reaction rate of the esterification or transesterification reactions. In order to counteract the kinetics of the reaction, and to obtain reasonable dwell times in the processing facilities, the esterification or transesterification is carried out in currently customary methods at high temperatures, and accelerated through the use of catalysts. By way of example, a method taken from DE 102 51 984 A1 is referenced at this point, which provides for a conversion at 190-240° C. in the presence of a tetra-alkyl titanate catalyst in 18 hours. Lower temperatures result in significantly longer dwell times, which cannot be tolerated in conventional processing facilities.